Selected Vehicle Safety Systems at a Glance

Selected Vehicle Safety Systems at a Glance

Vehicle Technology

Jun 2017

Accident researchers and road safety experts all agree that the number of accident victims can be dramatically reduced with the support of driver assistance systems. On the one hand, the biggest possible market penetration is essential here. But even when supported by additional safety systems, drivers still have to drive in a manner appropriate to, among other things, the road and visibility conditions. After all, even with the best, most advanced systems, drivers cannot shift the boundaries of physics. On the other hand, a whole range of basic preconditions has to be met to ensure that the systems function effectively – including, for example, a functioning brake system (mechanics, hydraulics/pneumatics, sensors, actuators and electronics). Additionally, the systems must not be disabled. Some systems operate at whatever speed the car is traveling, others just at certain speeds. Below are brief descriptions of how selected assistance systems function. The system names and functional scopes designated by the manufacturers may differ from those used below. Drivers are advised to always carefully read the instructions before enabling these systems.

Antilock Braking System (ABS)

This system allows emergency braking on road surfaces with different levels of grip without the driver losing control of the steering or the vehicle skidding. Any excessively sudden drop in the rotational speed of a wheel is indicative of impending wheel lock. The system detects an impending wheel lock and starts to modulate the brake pressure. Here, the wheel slip is regulated close to the optimum value, whereby vehicle deceleration is maintained at the maximum level according to the available frictional connection between the tires and road surface and, at the same time, sufficient lateral force for steering and stabilization is still available. ABS allows the driver to steer the vehicle with stable changes in direction despite applying full braking power. Even when negotiating bends, the driver can still apply full braking power, thereby ensuring maximum deceleration – within physical limits – without the vehicle starting to skid.

Brake Assist System (BAS)

The BAS reduces the braking distance in emergency situations if, at a critical moment, the driver does not apply the brakes hard enough. In such situations, the system automatically develops maximum brake boost within fractions of a second, thereby significantly reducing the vehicle’s stopping distance. The BAS also detects a driver’s intention to execute an emergency braking maneuver on the basis of the speed with which the driver initially presses the brake pedal. If the risk of a collision has been detected, more advanced systems increase the pressure in the braking system before the driver presses the brake pedal so that the driver, when pressing the brake pedal, immediately induces the full braking pressure in the wheel brake cylinder. This helps to reduce the “brake threshold duration”, thereby cutting the braking distance short by valuable meters.

Electronic Stability Control (ESC)

ESC acts on the vehicle’s drive and braking system and can help drivers to maintain control over their vehicle in critical situations. The associated control unit uses sensors to continuously monitor the vehicle’s driving dynamics. If any impending oversteer/understeer is detected, it brakes one, some or all of the vehicle’s wheels and, if necessary, intervenes in the engine management system. This means that the system is capable of detecting typical hazardous situations and, in response, helping drivers to maintain control over their vehicle within the limits of what is physically possible. The severity of accident scenarios such as skidding during rapid cornering or on slippery road surfaces and sudden evasive maneuvers can be reduced and the resulting accident risk considerably minimized.

Adaptive Cruise Control (ACC)

Constant braking and acceleration and frequent lane changes are part and parcel of everyday driving on congested roads. For this reason, most people do not stick to the “half of the speed indicator” rule – a rule of thumb used for determining the safe distance from the car in front – with the resulting risk of rear-end collisions. The intelligent cruise control system with a front distance sensor and distance control automatically adjusts the vehicle speed during moderate deceleration of around 3m/s² in keeping with the traffic flow in order to ensure that a safe distance from vehicles ahead is maintained. If the vehicle ahead brakes suddenly, the system issues a visual and audible warning, additionally allowing the driver to respond. Advanced ACC systems can slow the vehicle right down to a standstill and also move the vehicle off from standstill (follow-to-stop and stop-and-go function).

Advanced Emergency Braking System (AEBS)

This anticipatory emergency braking system is based on adaptive cruise control systems and is designed to prevent rear-end collisions or at least reduce the collision speed in order to signififificantly reduce the severity of the collision. The driver is alerted of an impending collision with the vehicle in front in a multi-stage process involving a visual and/or acoustic and/or haptic signal. The haptic signal, for example, could take the form of an initial application of the brakes. If the driver does not respond and the situation is becoming ever more critical, partial braking is automatically initiated during the course of the subsequent warning cascade. If the driver still fails to respond, advanced systems are also capable of automatically initiating full vehicle braking. Some systems respond not only to other motor vehicles, but also cyclists and pedestrians.

Lane Departure Warning (LDW)/Lane Keeping Support (LKS)

These systems can alert drivers traveling on rural roads or highways – i.e. outside urban areas – of when the vehicle drifts out of its lane. An additional function also keeps the vehicle in the middle of the lane, even on wide bends. This is a valuable aid particularly on long, monotonous stretches of road when drivers are prone to falling levels of alertness. A video camera installed behind the windshield captures the road markings and a downstream electronic system analyzes the course of the lane. More advanced systems can also compensate – to an extent – for missing or poor road markings. If the system detects that the driver is moving the vehicle out of the lane without having activated the turn signal, it outputs side-dependent visual and/or acoustic and/or haptic signals. The steering wheel can draw attention to itself with a gentle movement, giving the driver enough time to correct the vehicle’s course. Course corrections are also possible through gentle braking of individual wheels.

Blind Spot Monitoring/Lane Change Assist (LCA)

Vehicles approaching on the driver’s side and rear – an area (partially) invisible to the driver (passing lane/parallel lane) – are recorded by sensors and signaled to the driver. If the driver intends to change lane despite the risk of a collision, the driver is alerted so that a crash can be avoided. The blind spot is now nothing to be afraid of – although it is essential that drivers still take the time to glance over their shoulders.

Attention Assist/Driver Alert

This system uses a range of sensors and signal evaluation algorithms to permanently monitor driver behavior. Verified indicators of declining concentration and impending drowsiness include unusual steering motions and blinking intervals. The system can combine data on the type and frequency of these responses with other data such as vehicle speed, journey duration or time of day to calculate the degree of fatigue. If the system detects that the driver is drowsy, the driver is alerted to this with visual and/or acoustic and/ or haptic signals and advised to take a break.

Head-up display (HUD)

This display system projects information that is important to the driver directly into the driver’s field of vision. The head-up display means that the driver no longer has to take their eyes off the road in order to see the information – such as vehicle speed, information provided by the traffic sign recognition system or any pedestrians or cyclists detected by the night vision system – displayed on the instrument cluster. This can help to provide a valuable increase in reaction time in hazardous situations.

Adaptive Frontlighting Systems (AFS)

In Germany, around 20% of road accidents resulting in personal injury and 30% of fatal accidents occur at night. State-of-the-art light systems improve visibility, thereby helping to reduce the risk of accidents at night. Xenon and high-performance LEDs can already be found in conventional headlights to ensure that the light ahead of the vehicle is distributed more effectively. Equipped with the corresponding functional scope, the systems provide optimum light distribution for the driver at all times depending on the speed, surroundings and course of the road; in addition, intelligent technology prevents drivers of oncoming vehicles from being dazzled. With dynamic curve lighting, for example, the headlamps automatically swivel in line with the course of the road, thereby allowing drivers to better see the course of the curve ahead and react more quickly to potentially critical situations. If the curves are particularly tight or the driver intends to turn off, the static turning light ensures greater visibility. The light emitted by the Adaptive Frontlighting System (AFS) replaces the conventional functions of the static lower beam, whereby the light is automatically adjusted on the basis of the speed as well as other parameters such as the surrounding conditions in urban traffic, on country roads or highways and bad weather. If the system detects that other road users will not be dazzled by the lights, it automatically sets full illumination of the road, if necessary up to the intensity of upper beam. But here, too, responsibility lies with the driver, who may have to take sudden action to switch to the static lower beam.

Night vision assist

Visibility is greatly reduced at night, especially when the situation does not allow the upper beam to be used. If it is also raining or foggy, it can be almost impossible to discern the road ahead. Pedestrians or cyclists traveling without lights along the side of the road are often spotted too late by drivers, as too are wild animals that stray onto the road without warning. The night vision assist system can help to mitigate these hazards. It uses one or more infrared cameras to observe the road and presents an image of what it can see on the road ahead on a screen. In this high-contrast electronic image, humans and animals are clearly visible against the background. The night vision assist system is even unaffected by the dazzling lights of an oncoming car. Systems from the second generation of development can evaluate image patterns to detect pedestrians, cyclists and even wild animals and provide appropriate warning for drivers with visual/acoustic signals. Even more effective are marking light pulses above the headlights directly in the detected hazard zone ahead of or next to the vehicle.

Seatbelt reminder

If a vehicle occupant fails to put on their seatbelt and the vehicle is moving at a specific (low) speed, the seatbelt reminder system issues a visual and/or acoustic warning. And not without reason, because wearing a seatbelt – ideally also featuring a tensioner and load limiter – is the ultimate precondition for the passive safety of vehicle occupants and, as such, the number one lifesaver. Experts recommend seatbelt reminders for both the front and rear seats.